Method for producing a head core slider

ABSTRACT

A head core slider for a rigid magnetic disk drive, and a method of producing the same. The core slider includes a slider body, a track portion, a yoke portion and a narrow stepped portion. The slider body has two spaced-apart parallel air bearing portions, and the track portion is formed integrally with at least one of the bearing portions, so as to extend from one end of the bearing portion in the direction of length of the bearing portion. The track portion has the same height as the bearing portion, and a width smaller than that of the bearing portion. The yoke portion is formed integrally with the track portion, so as to extend from one end of the track portion remote from the bearing portion, and has a protrusion of the same height as the track portion. The width of the protrusion is smaller than that of the bearing portion and larger than that of the track portion. The stepped portion is formed so as to surround at least the track portion and the protrusion of the yoke portion, and has a surface which is spaced apart from top surfaces of the track portion and the protrusion by a distance nearly equal to the predetermined height. The bearing, track and stepped portions and the protrusion are formed by etching the surfaces of two bonded ferrite blocks, through an etching mask pattern corresponding to the desired configuration to be formed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to improvements in a floating-type coreslider of a magnetic head for a rigid magnetic disk drive.

2. Discussion of the Prior Art

In the art of a rigid magnetic disk drive (sometimes abbreviated as"RDD"), there is known a floating-type magnetic head which employs abulk type core slider, such as a monolithic type slider as indicatedgenerally at 1 in FIG. 1. This core slider 1 is an integral structureconsisting of a slider body 2, and a yoke portion 3 which is generallyC-shaped in cross section. On one surface of the slider body 2 on whicha recording medium in the form of a magnetic disk slidably rotates,there are formed a pair of parallel spaced-apart air bearing portions4a, 4b which extend in the rotating or sliding direction of the magneticdisk. The sliding surfaces of the air bearing portions 4a, 4b have asuitable height as measured from a recessed portion therebetween. Thecore slider 1 has a center rail 5 which is formed between the airbearing portions 4a, 4b so as to extend parallel to the air bearingportions. The center rail 5 serves as a track portion whose surface hasthe same height as the air bearing portions 4a, 4b. In operation, theselected recording track of the magnetic disk is aligned with the trackportion or center rail 5. The yoke portion 3 indicated above is formedintegrally with the slider body 2, at one of opposite ends of the centerrail 5. The yoke portion 3 and the slider body 2 cooperate with eachother to define a closed magnetic path for the magnetic head.

The monolithic type core slider 1 formed solely of a ferrite material isrlatively economical to manufacture. The width of the elongate trackportion is determined by tapering or chamfering the parallel edges ofthe center rail 5. This manner of forming the track portion suffers fromdifficulties in precisely establishing the desired track width, and inreducing the track width. Further, when the core slider 1 is moved offthe surface of the magnetic disk, both air bearing portions 4a, 4bshould lie within the range of radius of the magnetic disk. Namely, thecenter rail or track portion 5 located between the two air bearingportions 4a, 4b should be positioned a given distance away from theouter periphery of the magnetic disk in the radially inward direction.Therefore, the effective recording surface area of the magnetic disk isreduced to an extent corresponding to the distance between the trackportion 5 and the air bearing portion 4a, 4b. In other words, the datastorage capacity of the magnetic disk is limited by the construction ofthe core slider 1.

There is also known a composite type core slider which is produced by aslider body and a head core which are separately prepared. Morespecifically, a ferrite core having a track portion formedperpendicularly to a surface thereof is partially embedded in and fixedto a non-magnetic slider body. This composite type core slider isadvantageous over the monolithic type, in that the track portion can beformed with its width accurately controlled to a desired value, and thatthe width can be made relatively small. The composite type is furtheradvantageous in that the track portion can be formed in alignment withan air bearing portion, i.e., formed on a line of extension of the airbearing portion, whereby the outer peripheral portion of the magneticdisk can be used as an effective recording area. However, the compositetype core slider is disadvantageous in the cost of manufacture, becauseof the steps of separately preparing the slider body and the core, andthen joining these two members together.

A further type of core slider is proposed according to laid-openPublication No. 62-18615 of unexamined Japanese patent application, inan attempt to lower the cost of manufacture while enjoying thefunctional advantages of the composite type discussed above. In thisproposed core slider, a yoke portion is formed integrally with a sliderbody, at one end of an air bearing portion formed on the slider body,such that the yoke portion and the slider body cooperate to constitute ahead core which has a magnetic gap. To produce this core slider, groovesdefining a track portion are formed in appropriate two blocks, and thetwo blocks with the grooves filled with a glass material are buttedtogether and bonded by the glass material, such that selected parts ofthe joining surfaces define the magnetic gap therebetween. Subsequently,the obtained body of the bonded blocks is subjected to a groovingoperation to form the air bearing portion and the yoke portion.

In the core slider of the type described above, the track portion is inline with the air bearing portion, and therefore these two portions maybe concurrently formed by the grooving operation, contrary to the airbearing and track portions of the monolithic type core slider which arespaced apart from each other. However, this type of core slider requiresthe step of establishing the desired width of the track portion by thegrooving operation, and an additional step of filling the grooves withthe glass material, and consequently suffers from a relatively increasedtotal number of process steps, which counterbalances the advantage ofthe concurrent formation of the track and air bearing portions. Inaddition, the cross sectional area of the yoke portion of the coreslider in question tends to be larger than that of the composite typecore slider and the monolithic type core slider of FIG. 1. This resultsin an increase in the inductance of the head core, which isdisadvantageous in performing high-frequency recording operations on themagnetic disk. That is, the core slider is not capable of assuringsufficiently high density of recording per unit area of the magneticdisk.

For producing the conventional core slider as shown in FIG. 1 whereintwo spaced-apart air bearing portions and a center rail are provided,the grooving operations to form the air bearing portions and center railand the chamfering operations to determine the width and length of theformed bearing portions and rail are performed by using a grinding wheelsuch as a diamond wheel. The grooving and chamfering operations requirea total of eight grinding passes for each core slider, and are the mosttime-consuming steps of the process. Further, the error in the widths ofthe air bearing portions and track portion (center rail) cannot be heldwithin a permissible range of ±3 microns, due to unavoidable positioningerror of the grinding wheel, and due to inevitable variations in thethickness or height of the blank for the slider body and positioningerror of the yoke portion bonded to the slider body blank. Moreover, thesurfaces finished by the diamond wheel inevitably suffer from chippingof one micron or more.

SUMMARY OF THE INVENTION

It is therefore a first object of the present invention to provide ahead core slider for a rigid magnetic disk drive, which has no chamferedportions at the trailing end and which is adapted to effectively protectits track portion and a magnetic disk against damage and to provide ahead core having a relatively low inductance, for thereby permitting ahigh-frequency recording operation on the magnetic disk, in order toincrease the recording density per unit area of the disk.

It is a second object of the present invention to provide an improvedmethod of producing such a head core slider in an economical manner,with a reduced number of process steps, as compared with theconventionally available methods.

The first object may be achieved according to one aspect of the presentinvention, which provides a head core slider for a rigid magnetic diskdrive, comprising a slider body, a track portion, a yoke portion and anarrow stepped portion. The slider body has a pair of parallel airbearing portions which are spaced apart from each other in a firstdirection and each of which has a predetermined height and a first widthin the first direction. The track portion is formed integrally with atleast one of the parallel air bearing portions, so as to extend from oneof opposite ends of the air bearing portion in a second directionsubstantially perpendicular to the first direction. The track portionhas the same height as the air bearing portion, and a second widthsmaller than the first width. The yoke portion is formed integrally withthe slider body and the track portion, so as to extend from one end ofthe track portion remote from the air bearing portion in the seconddirection. The yoke portion has a protrusion which has the predeterminedheight and a third width which is smaller than the first width andlarger than the second width. The slider body, the yoke portion and thetrack portion cooperate with each other to form a magnetic head corewhich has a closed magnetic path, the stepped portion is formedextending so as to surround at least the track portion and theprotrusion of the yoke portion. The stepped portion has a surface whichis spaced apart from top surfaces of the track portion and theprotrusion in a third direction perpendicular to the first and seconddirections, by a distance corresponding to the predetermined height.

The second object indicated above may be attained according to anotheraspect of the invention, which provides a method of producing a headcore slider for a rigid magnetic disk drive, comprising the followingsteps. (i) A first ferrite block which gives a slider body, and a secondferrite block which gives a yoke portion are prepared and buttingtogether into an integral ferrite bar which defines a closed magneticpath having a magnetic gap. (ii) An etching mask is formed on a surfaceof the integral ferrite bar, the etching mask having a pattern whichcorresponds to a configuration formed on the surface of the integralferrite bar. The configuration includes (a) a pair of parallel airbearing portions provided on the slider body such that the air bearingportions are spaced apart from each other in a first direction each ofthe air bearing portions having a first width in the first direction,(b) a track portion formed integrally with at least one of the pair ofparallel air bearing portions, so as to extend from one of opposite endsof the air bearing portion in a second direction substantiallyperpendicular to the first direction, the track portion having a secondwidth smaller than the first width, and (c) a protrusion provided on theyoke portion such that the protrusion extends from one end of the trackportion remote from the air bearing portion in the second direction, theprotrusion having a third width which is smaller than the first widthand larger than the second width. (iii) At least the surface of theintegral ferrite bar is etched, via the etching mask, so as to producethe configuration corresponding to the pattern of the etching mask, suchthat the pair of air bearing portions of the slider body, the protrusionof the yoke portion, and the track portion between the bearing portionand the protrusion have a same predetermined height. (iv) The etchedintegral ferrite bar is cut into a plurality of pieces each of whichserves as the head core slider, such that the each piece having theslider body, the yoke portion and the track portion is provided with anarrow stepped portion extending so as to surround at least the trackportion and the protrusion of the yoke portion. The stepped portion hasa surface which is spaced apart from top surfaces of the track portionand the protrusion in a third direction perpendicular to the first andsecond directions, by a distance corresponding to the predeterminedheight.

A magnetic head for a rigid magnetic disk drive is obtained by winding acoil on the head core slider of the present invention constructed asdescribed above. The magnetic head is moved between a first position inwhich the sliding surface of the core slider contacts the surface of themagnetic disk, and a floating or second position in which the slidersurface is spaced from the surface of the disk. In operation of themagnetic disk drive, it is important that the magnetic disk be protectedagainst damage upon movements of the magnetic head to and from the firstand second positions to effect and release the contact between the coreslider and the disk. This damage of the magnetic disk depends upon thesurface conditions of the core slider, more specifically, the surfaceconditions of the air bearing portions and the track portion, and uponthe edge configuration of these bearing and track portions. If thesurface conditions are poor, not only the disk but also the core slidermay be damaged.

According to the present invention, the surface of the ferrite bar blankon the side of the magnetic disk is first ground to sufficiently highdegrees of smoothness and straightness, and then an etching mask of asuitable material such as a photoresist is formed on the ground surfaceof the ferrite bar blank, in a pattern corresponding to the desiredraised configuration including the air bearing portions, track portionand yoke portion. The surface of the ferrite bar blank is then subjectedto an etching process, whereby the air bearing and track portions areformed with high degrees of surface smoothness and straightness. Thus,the conventionally experienced damage of the magnetic disk is avoided.Further, the substantially entire surface area of the magnetic disk canbe utilized for storing information, because of the alignment of thetrack portion with the air bearing portion, whereby the effectiverecording capacity of the magnetic disk can be increased when themagnetic head uses the instant core slider.

Furthermore, the provision of the relatively wide protrusion which is inline with the track and air bearing portions and has the same height asthese portions is effective to protect the relatively narrow trackportion against damage upon movements of the magnetic head to and fromthe first and second operating positions indicated above.

Moreover, the narrow stepped portion provided around the track portionand the protrusion protects the track portion and protrusion againstchipping thereof during cutting operations on the ferrite bar to removethe ferrite material surrounding the yoke portions and to cut the barinto the individual core sliders. In other words, there arises noproblem even if the stepped portion chips during the cutting operations.Further, the instant core slider does not require a chamfered portion atits trailing end as viewed in the rotating direction of the disk.

In addition, the width of the yoke portion is made smaller than that ofthe air bearing portion, for reducing the cross sectional area of themagnetic path and thereby lowering the inductance of the magnetic head,so as to permit high-frequency recording operation on the magnetic disk.That is, the instant head core slider provides for an increased densityof information recorded per unit area of the magnetic disk.

According to the method of the present invention, the etching process isutilized to form the desired configuration of the air bearing portions,track portions and yoke portions on the ferrite bar, with highdimensional accuracy. Consequently, the required number of process stepsis significantly reduced, and the cost of manufacture of each coreslider is accordingly lowered.

In one preferred form of the present invention, corners of each airbearing portion at its trailing end, and corners of the correspondingtrack portion at its trailing end are rounded to desired radii ofcurvature. Further, the connections between the track portion and theair bearing portion and yoke portion may be similarly rounded orchamfered or inclined. These rounded corners and connections and/orchamfered connections are effective to protect the track portion and themagnetic disk against damage upon movements of the magnetic head withrespect to the magnetic disk. It is noted that these rounded and/orchamfered parts may be also formed in the etching process.

According to the present method of the invention wherein the etchingprocess is used to form the air bearing, track and yoke portions, theangle of the side surfaces of these raised portions with respect totheir top surfaces may be suitably controlled so as to provide anadequate compromise between the mechanical strength and the functionalcapability. The instant method does not require any machining operationsto establish the desired dimensions (such as width) and profile of theindividual portions of the head core slider, and is therefore free fromthe chipping problem experienced in the art. Where ferrite singlecrystals are used for the ferrite blocks, the above-indicated angle ofinclination may be suitably held within a range of 65° and 80°, by usingthe crystal plane (100) as the surface of each block defining themagnetic gap, and the crystal plane (110) as the surface on which theair bearing and other portions are formed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and optional objects, features and advantages of the presentinvention will be better understood by reading the following detaileddescription of a presently preferred embodiment of the invention, whenconsidered in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view showing one example of a known monolithichead core slider for a rigid magnetic disk drive;

FIG. 2 is a perspective view of two ferrite blocks which are bondedtogether;

FIG. 3 is a perspective view of an integral ferrite structure preparedby bonding the two ferrite blocks of FIG. 2;

FIG. 4 is a perspective view of two ferrite bars prepared by cutting theferrite structure of FIG. 3;

FIG. 5 is an end elevational view showing one of the two ferrite bars ofFIG. 4, after the disk sliding surface of the ferrite bar is ground;

FIG. 6 is a fragmentary plan view showing the ferrite bar of FIG. 5,after an etching mask is formed on the ground surface;

FIGS. 7 and 8 are fragmentary plan and elevational views of the ferritebar which has been subjected to an etching process;

FIG. 9 is a fragmentary plan view of the etched ferrite bar, showingcutting lines along which the bar is cut to obtain a desired dimensionin the direction perpendicular to the cutting lines;

FIG. 10 is a fragmentary plan view showing the ferrite bar, after achamfered surface is formed at the leading end portion of each airbearing portion;

FIG. 11 is a fragmentary plan view of the ferrite bar, after yokeportions are formed by cutting off the appropriate portions of the bar;

FIG. 12 is a fragmentary plan view showing cutting lines along which theferrite bar of FIG. 11 is cut to obtain a single head core slider;

FIG. 13 is a plan view of the head core slider produced by cutting ofthe ferrite bar of FIG. 12;

FIG. 14 is an enlarged fragmentary view showing the trailing end portionof the head core slider of FIG. 13; and

FIG. 15 is an elevational view taken in the direction of A--A of FIG.14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

To produce a head core slider for a rigid magnetic disk drive, a firstand a second ferrite block are prepared. The first ferrite block is usedto provide a slider body of the head core slider, while the secondferrite block is used to provide a yoke portion of the head core slider.These ferrite blocks are formed of a conventionally used ferritematerial having a high degree of permeability. The ferrite blocks aregenerally elongate rectangular members having suitable thicknesses. Theelongate ferrite blocks are butted and bonded together into an integralferrite structure, from which two or more magnetic head cores areproduced. The magnetic head core has a closed or annular magnetic path.The ferrite blocks having a high degree of permeability may consist ofsingle crystals or polycrystalline structures of Mn-Zn ferrite or Ni-Znferrite, or may be a composite structure consisting of a single crystalferrite portion and a polycrystalline ferrite portion. Where a ferritesingle crystal is used for the ferrite block, one of the crystal planes(100), (110), (311), (332), (611) and (211) is used as an air bearingsurface of the head core slider (as a sliding surface on which amagnetic disk slides).

Referring to FIG. 2, the first and second ferrite blocks are illustratedat 10 and 12, respectively, by way of example. At least one of the firstand second ferrite blocks 10, 12 has at least one coil groove 14 forwinding a coil on a head core slider produced from the ferrite blocks.Each coil groove 14 is formed in one of opposite surfaces of theappropriate ferrite block 10, 12, in the longitudinal direction of theblock. In this specific example of FIG. 2 wherein two head core slidersare prepared from the first and second ferrite blocks 10, 12, two coilgrooves 14 are formed in both of the first and second ferrite blocks 10,12 in the corresponding portions of the surfaces which define magneticgaps of the prepared head core sliders, as described below. Between thetwo coil grooves 14, 14 in each of the ferrite blocks 10, 12, a centergroove 16 is formed so as to extend parallel to the coil grooves 14.This center groove 16 is used to allow air to leak during a process offilling the magnetic gap with a glass material (which will be describedhereinafter).

Elongate surface areas 10a left between the coil grooves 14 and thecenter groove 16 of the first ferrite block 10, and/or elongate surfaceareas 12a left between the coil grooves 14 and the center groove 16 ofthe second ferrite block 12, are subjected to an etching or othersuitable process in which a suitable amount of stock is removed todefine the above-indicated magnetic gaps, whose depth is indicated bycharacter "l" in FIG. 5. It is desirable that the first and secondferrite blocks 10, 12 have different lengths, as indicated in FIG. 2,for facilitating the reading of the gap depth "l" when a surface 20(FIG. 5) of each ferrite bar 18 (FIG. 4) obtained from the ferriteblocks 10, 12 is ground so as to establish the desired gap depth "l".

The first and second ferrite blocks 10, 12 each having the two coilgrooves 14 and the single center groove 16 formed as described above arethen butted together as shown in FIG. 3 such that the grooves 14, 16 inthe two ferrite blocks 10, 12 are aligned with each other so as to formchannels extending in the longitudinal direction of the blocks. Thebutted first and second ferrite blocks 10, 12 are bonded into anintergral ferrite structure, by a known solid reaction bonding method, asintering method or other suitable bonding method. Subsequently, thegaps formed adjacent the center grooves 16 are filled with a suitableglass material which is introduced in a molten state through theabove-indicated channels, so that the gaps are protected during thefollowing steps of manufacture.

The prepared integral ferrite block 10, 12 is cut along the centergrooves 16, into two ferrite bars 18, 18 as shown in FIG. 4. Eachferrite bar 18 has the channel 14.

The surface 20 which becomes a disk sliding surface of the finallyobtained head core slider is ground so as to establish the desired depth"l" of the gap, as indicated in FIG. 5. This grinding process is alsonecessary to improve the adhesion of an etching mask 22 to the surface20, when the mask 22 is formed in the following step, as indicated inFIG. 6, to form air bearing portions 24, track portion 26 andprotrusions 28 (FIG. 7) of each head core slider eventually obtainedfrom the ferrite bar 18, as described below. The grinding of the surface20 also assures uniform amount of stock removal of the ferrite materialover the non-masked portions of the ferrite bar 18.

As indicated above, the etching mask 22 is then formed on the groundsurface 20, in a pattern corresponding to the configuration of the airbearing portions 24, track portion 26 and protrusions 28 of each headcore slider. Described more specifically referring to FIG. 7, the airbearing portions 24 are formed parallel to each other in the directionperpendicular to the longitudinal direction of the ferrite bar 18, andare spaced apart from each other in the longitudinal direction of theferrite bar 18. Each air bearing portion 24 has a predetermined heightfrom the surface 20, and a predetermined width in the longitudinaldirection of the ferrite bar 18. The track portion 26 is formedintegrally with one end of each air bearing portion 24, so as to extendfrom the air bearing portion in the direction perpendicular to thelongitudinal direction of the ferrite bar 18. The track portion 26 hasthe same height as the air bearing portion 24, and a width smaller thanthat of the air bearing portion 24. The protrusion 28 extends from oneend of the track portion 26 remote from the air bearing portion 24 inthe direction perpendicular to the longitudinal direction of the ferritebar 18. The protrusion 28 has the same height as the air bearing andtrack portions 24, 26, and a width which is smaller than that of the airbearing portion and larger than the width of the track portion 24.

The etching mask 22 is formed by a suitable known method such as ascreen printing technique, which is selected to meet the requiredforming accuracy and economy. In particular, a photoetching method usinga photoresist is preferably practiced for relatively high patternforming accuracy and relatively easy formation of the masking pattern.In this case, for example, the surface 20 of the ferrite bar 18 isentirely covered by a photoresist layer, and the portions of thephotoresist layer which correspond to the above-indicated portions 24,26 and protrusions 28 are removed to expose the corresponding portionsof the surface 20 of the bar 18. The etching mask 22 may be formed of apositive or negative type photoresist, or formed of a suitable metallicmaterial such as Cr, or SiO or SiO₂, by vacuum vapor deposition,sputtering, chemical vapor deposition (CVD) or other technique. Themethod of forming the mask 22 and the material of the mask 22 aresuitably selected in terms of the ease and cost of formation, and theadhesiveness of the mask 22 to the surface 20.

The ferrite bar 18 partially covered by the etching mask 22 is thensubjected to an etching process to remove a suitable amount of stockfrom the non-masked portions of the surface 20. As a result, theportions 24, 26, 28 covered by the etching mask 22 are left unremoved asshown in FIGS. 7 and 8. These portions serve as the air bearing portion24, track portions 26 and protrusions 28, which have been described. Theferrite bar 18 is usually etched by an ordinary electrolytic etching orchemical etching method, preferably by using an aqueous solutionconsisting of water and the balance principally consisting of phosphoricacid, as disclosed in Japanese patent application No. 60-222388 (laidopen in 1987 under Publication No. 62-XXXXXX). With the ferrite bar 18thus etched, inclined surfaces 30 are further formed surrounding the airbearing portions 24, track portions 26 and protrusions 28.

The etched ferrite bar 18 is then cut parallel to its longitudinaldirection, for instance, at cutting lines indicated at 32, 34 in FIG. 9,in order to determine the length of each eventually obtained head coreslider, as measured in the longitudinal direction of the air bearingportions 24. Subsequently, the leading end portion of each air bearingportion 24 is cut to form a chamfered portion or leading ramp 36, asindicated in FIG. 10. This chamfered portion 36 is inclined at anadequate angle relative to the top surface of the air bearing portion24. Then, the portions of the ferrite bar 18 which surround the trailingend portions of the air bearing portions 24, track portions 26 andprotrusions 28 are removed so as to form yoke portions 38 which includethe protrusions 28, as illustrated in FIG. 11. However, a suitableamount of the ferrite stock is left unremoved adjacent the periphery ofthe yoke portions 38. Each yoke portion 38 has a magnetic gap and anaperture corresponding to the coil grooves 14.

Subsequently, the ferrite bar 18 is cut parallel to the air bearingportions 24, at parallel cutting lines as indicated at 40, 40 in FIG.12, such that each cut segment which constitutes a head core slider 42as shown in FIG. 13 includes the two air bearing portions 24.

As shown in FIG. 13, the head core slider 42 includes a slider body 44provided with the two parallel air bearing portions 24, and the two yokeportions 38 each having the protrusion 28 which has the same height asthe air bearing portions 24 on the slider body 44 and the width smallerthan that of the air bearing portions 24. Between the trailing end ofeach air bearing portion 24 and the protrusion 28 of the yoke portion38, the track portion 26 having the width smaller than the protrusion 28is formed so as to bridge the air bearing portion 24 and the yokeportion 38. As indicated in FIG. 14, a relatively narrow stepped portion46 is left along the two outer sides of each air bearing portion 24, andso as to surround the corresponding track portion 26 and yoke portion38. It will be understood that this stepped portion 46 has the etchedsurface of the ferrite bar 18, and that the above-indicated height ofthe portions 24, 26, 28 is measured with respect to the flat portion ofthe stepped portion 46, as indicated in FIG. 15.

As depicted in detail in FIGS. 14 and 15, each of the head core sliders42 produced according to this embodiment of the invention includes apair of raised sections each of which consists of the slider body 44,track portion 26 and yoke portion 38. The slider body 44 has the twoparallel air bearing portions 24 which are spaced apart from each otherin a first direction and each of which has a predetermined height fromthe stepped portion 46 and a first width as measured in the firstdirection. The track portion 26 is formed integrally with thecorresponding air bearing portion 24, so as to extend from the end ofthe air bearing portion 24 remote from the chamfered portion 36, in asecond direction perpendicular to the first direction. The track portion26 has the same height as the air bearing portion 24, and a second widthwhich is smaller than the first width of the air bearing portion 24. Theyoke portion 38 is formed integrally with the slider body 44 and thetrack portion 26, so as to extend from the end of the track portion 26remote from the air bearing portion 24, in the second directionindicated above. The yoke portion 38 includes the protrusion 28 whichhas the same height as the air bearing portion and track portion 24, 26,and a third width which is smaller than the first width of the airbearing portion 24 and larger than the second width of the track portion26. The slider body 44, the track portion 26 and the yoke portion 38cooperate with each other to form a magnetic head core which has aclosed magnetic path. The stepped portion 46 is left so as to partiallysurround the air bearing portion 24, and totally surround the track andyoke portions 26, 38. The stepped portion 46 has the flat part which isspaced apart from the top surfaces of the track and yoke portions 26,38, by a distance nearly equal to the height of the portions 24, 26, 28.In the instant head core slider 42, the relative wide protrusion 28 ofthe yoke portion 38 is effective to protect the relative narrow trackportion 26 against damage due to contact with a rigid magnetic disk whenthe disk is moved to the position for contact with the head core slider42. Further, the width of the yoke portion 38 is selected to be smallerthan that of the air bearing portion 24, for reducing the crosssectional area of the yoke portion 38 and thereby lowering itsinductance and thereby permitting high-frequency recording ofinformation on the magnetic disk, for increased density of recording perunit area of the disk.

In the instant core slider 42, corners 48 at the trailing end of the airbearing portion 24 and corners 50 at the trailing end of the protrusion28 are rounded to suitable radii of curvature, to avoid right-angleedges at the corners, whereby damages of the magnetic disk and theslider 42 due to their contact may be significantly reduced.

Further, connections 52 between the track portion 26 and the air bearingportion 24, and connections 54 between the track portion 26 and theprotrusion 28 are inclined or chamfered to avoid right-angle edges atthe connections. This arrangement increases the strength of the trackportion 24 at its end portions adjacent the air bearing portion 24 andthe protrusion 28. The inclination or chamfer angle of the connections52, 54 with respect to the longitudinal direction of the air bearingportion 24 is preferably within a range between 30° and 60°. While theconnections 52, 54 may be rounded, the inclined configuration ispreferred in this specific head core slider 42.

The air bearing portion 24, track portion 26 and protrusion 28 consistof a raised section which is left unremoved during the etching processof the ferrite bar 18, as described before. This raised section isformed with the inclined surfaces 30 indicated above, as depicted inenlargement in FIG. 15. The inclination angle β of the inclined surfaces30 with respect to the top surfaces of the portions 24, 26 andprotrusion 28 is preferably within a range between 45° and 80°, morepreferably within a range between 60° and 75°. If this angle β isexcessively large, the portions 24, 26 and protrusion 28 have sharpedges which easily chip. If the angle β is excessively small, therearises a problem with the track portion 26. Namely, the effectiverecording width of the magnetic head and the effective recording widthof the recording tracks of the magnetic disk are unfavorably increased,leading to a reduced recording density of the magnetic disk.

While the presently preferred form of the head core slider of theinvention for a rigid magnetic disk drive and the presently preferredmethod for producing the head core slider according to the inventionhave been described in detail by reference to the accompanying drawings,it is to be understood that the invention is not limited to the precisedetails of the illustrated embodiment, but may be embodied with variouschanges, modifications and improvements, which may occur to thoseskilled in the art, without departing from the spirit and scope of theinvention defined in the appended claims.

In the illustrated embodiment, the magnetic gap is formed in the trackportion 26 such that the parts of the opposed surfaces of the buttedfirst and second ferrite blocks 10, 12 define the magnetic gap. However,the principle of the present invention is also applicable to a compositemagnetic head core slider wherein a magnetic metal layer is formed on atleast one of the opposed surfaces of the ferrite blocks 10, 12, so as todefine a magnetic gap therebetween. This composite magnetic head coreslider is suitable for use with a recording medium which has a highdegree of coercive force. The magnetic metal layer or layers may beformed by a suitable known method, in the area 10a or 12a, or areas 10aand 12a of the ferrite blocks 10, 12, as indicated in FIG. 2. Theseparts of the ferrite surfaces may be roughed or undulated before themagnetic metal layer or layers are formed thereon. The desired width ofthe track portion is formed by etching the magnetic metal layer orlayers and the ferrite, such that the magnetic metal and the ferrite areetched at the same rate.

What is claimed is:
 1. A method of producing a head core slider for a rigid magnetic disk drive, comprising the steps of:preparing a first ferrite block from which a slider body is to be formed, and a second ferrite block from which a yoke portion is to be formed, and butting together said first ferrite block and said second ferrite block into an integral ferrite bar which defines a closed magnetic path having a magnetic gap; forming an etching mask on a surface of said integral ferrite bar, said etching mask having a pattern which corresponds to a configuration to be formed on said surface of said integral ferrite bar, said configuration including (a) a pair of parallel air bearing portions provided on said slider body which are spaced apart from each other in a first direction (b) a track portion formed integrally with at least one of said pair of parallel air bearing portions, so as to extend from one of opposite ends of said air bearing portion in a second direction substantially perpendicular to said first direction, said track portion having a second width smaller than a first width of each of said air bearing portions in said first direction and (c) a protrusion provided on said yoke portion which extends from one end of said track portion remote from said air bearing portion in said second direction, said protrusion having a third width which is smaller than said first width and larger than said second width; etching at least said surface of said integral ferrite bar, via said etching mask, so as to produce said configuration corresponding to said pattern of said etching mask, such that said pair of air bearing portions, said protrusion, and said track portion have a same predetermined height; and cutting the etched integral ferrite bar into a plurality of pieces each of which serves as said head core slider, such that each of said pieces which have said slider body, said yoke portion and said track portion is provided with a narrow stepped portion which surrounds at least said track portion and said protrusion, said stepped portion having a surface which is spaced apart from top surfaces of said track portion and said protrusion in a third direction perpendicular to said first direction and said second direction, by a distance corresponding to said predetermined height.
 2. A method of producing a head core slider for a magnetic disk drive, comprising the steps of:butting together a first and a second ferrite block to form a head core slider which defines a closed magnetic path having a magnetic gap; forming an etching mask on a surface of said head core slider which is interrupted by said magnetic gap, said etching mask having a pattern comprised of an area corresponding to a track portion to be formed across said magnetic gap having a width in the direction parallel to said magnetic gap which is greater than or equal to the width of said magnetic gap and areas corresponding to portions to be formed adjacent each end of said track portion, each of said portions being wider in said parallel direction than said track portion; and etching said surface of said head core to produce a configuration corresponding to said pattern.
 3. The method of claim 2, wherein said portions formed adjacent each end of said track portion consist of an air bearing portion and a protruding portion, respectively, which are spaced apart from each other by said track portion in a direction perpendicular to said parallel direction, said track portion having a second width which is smaller than a first width of said air bearing portion in said parallel direction, and said protruding portion having a third width which is smaller than said first width and larger than said second width in said parallel direction.
 4. The method of claim 3, further comprising chamfering an end of said air bearing portion remote from said track portion.
 5. The method of claim 3, further comprising rounding corners of an end of said air bearing portion adjacent said track portion and corners of an end of said protruding portion remote from said track portion.
 6. The method of claim 3, further comprising forming an inclination in a top edge of connections between said air bearing portion and said track portion, and between said track portion and said protruding portion, wherein an angle of said inclination with respect to top surfaces of said track portion, said air bearing portion and said protruding portion ranges from 45°-80°.
 7. The method of claim 2, wherein said protrusions formed adjacent each end of said track portion consist of an air bearing portion and a protruding portion, respectively, which are spaced apart from each other by said track portion in a direction perpendicular to said parallel direction, the method further comprising forming an inclination in a top edge of the periphery of said track portion, said air bearing portion and said protruding portion.
 8. The method of claim 7, wherein an angle of said inclination with respect to top surfaces of said track portion, said air bearing portion and said protruding portion ranges from 45°-80°.
 9. The method of claim 7, wherein an angle of said inclination with respect to top surfaces of said track portion, said air bearing portion and said protruding portion ranges from 60°-75°.
 10. The method of claim 1, further comprising chamfering an end of said air bearing portion remote from said track portion.
 11. The method of claim 1, further comprising rounding corners of an end of said air bearing portion adjacent said track portion and corners of an end of said protrusion remote from said track portion.
 12. The method of claim 1, further comprising forming an inclination in a top edge of connections between said air bearing portion and said track portion, and between said track portion and said protrusion, wherein an angle of inclination with respect to top surfaces of said track portion, said air bearing portion and said protrusion ranges from 45°-80°.
 13. The method of claim 1, further comprising forming an inclination in a top edge of the periphery of said track portion, said air bearing portion and said protrusion.
 14. The method of claim 13, wherein an angle of said inclination with respect to top surfaces of said track portion, said air bearing portion and said protrusion ranges from 45°-80°.
 15. The method of claim 13, wherein an angle of said inclination with respect to top surfaces of said track portion, said air bearing portion and said protrusion ranges from 60°-75°. 